Ruby

lexer.rb: ignore dedented space

• ext/ripper/lib/ripper/lexer.rb (on_heredoc_dedent): replace an
  empty string content because of dedentation with :on_ignored_sp.
  an empty token makes the sorted order unstable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59269 b2dd03c8-39d4-4d8f-98ff-823fe69b080e